This invention is concerned with a method of monitoring the positions of two movable side portions of a mould of a glassware forming machine which, in the operation of the machine, are moved in opposite directions into engagement with one another so that the side portions are in a mould-closed condition thereof in which they cooperate in defining a mould cavity in which molten glass can be moulded, and are subsequently moved apart to allow removal of moulded glass. While the invention is applicable to other types of glassware forming machines, it is particularly applicable to glassware forming machines of the individual section type.
Glassware forming machines of the individual section type are well known and comprise a plurality of individual glassware forming units, called sections, which are arranged side by side to receive gobs of molten glass from a common source and to feed their output to a common conveyor. Each section has a parison mould arrangement at which gobs of molten glass are formed into parisons either by a pressing operation or by a blowing operation, a blow mould arrangement in which parisons are blown to the shape of the required container, transferring means for transferring parisons from the parison mould arrangement to the blow mould arrangement, and take-out means for removing completed containers from the blow mould arrangement. In most glassware forming machines of the individual section type, both the parison mould arrangement and the blow mould arrangement of a section comprise two movable mould side portions. These movable side portions are moved in opposite directions either linearly or arcuately about a common vertical axis into engagement with one another so that the side portions are in a mould-closed condition in which they co-operate in defining a mould cavity. In the case of a mould of a parison mould arrangement, the mould cavity defines the shape of the parison and a gob of glass is introduced into the cavity and moulded to the shape of the cavity either by a blowing or by a pressing operation. In the case of a blow mould arrangement, the cavity receives a parison and the parison is blown to the shape of the cavity thereby forming the completed container. The mould portions are subsequently moved apart to allow removal of the parison from a parison mould arrangement or the completed article from a blow mould arrangement. In the case of linearly moved side portions, the portions are mounted on supports which are moved in opposite directions along a slideway. In the case of arcuately moved side portions, the side portions are mounted on supports which are both pivotally mounted on a common vertical axis and are swung in opposite directions about said axis.
It has been recognised that it is desirable to monitor the positions of the two movable side portions of a mould of a glassware forming machine to detect whether the mould portions reach their mould-closed condition. It is possible that, in the operation of the machine, a parison or a completed container may not be removed from the mould cavity as it should be with the result that, when the side portions approach their mould-closed condition, they are prevented from reaching that condition by the presence of glass in their line of movement. This undesirable condition can cause damage to the machine when molten glass is subsequently introduced into an unclosed mould and it is desirable to detect such conditions as soon as possible. Previous attempts to monitor the positions of the two movable side portions of a mould have included mounting transducers to monitor the movement of one of the side portions. However such transducers are relatively expensive and need to be protected from the hostile environment created by the presence of molten glass so that they have to be mounted in relatively inaccessible positions on the machine. Furthermore, it is not always sufficient to monitor the position of one only of the two movable side portions since the side portions may not meet at exactly the same position in every cycle of operation of the machine. For example, arcuately moved mould portions may meet at the exact centre line of the section or slightly to one side or the other side of said centre line. Attempting to monitor the positions of both movable side portions by means of transducers increases the abovementioned problems of expense and accessibility.
It is an object of the present invention to provide a method of monitoring the positions of two movable side portions of a mould of a glassware forming machine in which the side portions are monitored by inexpensive means that is readily accessible.